This proposal is a randomized clinical trial of a 12-week contingency management (CM) paradigm focused on the treatment of methamphetamine, amphetamine, and/or cocaine abuse in severely mentally ill (SMI) patients attending an urban community mental health center (CMHC), with a 26 week follow-up. Despite a great deal of interest in the treatment of co-occurring disorders, as well as in the growing problems of both methamphetamine (and its movement from more rural to urban settings) and cocaine abuse, there have been no published randomized trials of CM as the primary intervention for psycho-stimulant use disorders in the SMI population. The CM paradigm to be used is one which has been shown effective in several recent large clinical trials, using the variable magnitude of reinforcement procedure. The reinforcers will be vouchers or actual items useful for day to day living in this population. 200 SMI participants with co-occurring methamphetamine or cocaine abuse will be recruited from an urban CMHC and randomized to receive either the active CM paradigm plus treatment as usual (TAD), or TAU which will include the delivery of reinforcement for study involvement. The primary outcome is change in psycho-stimulant use (methamphetamine, amphetamine, and/or cocaine). Secondary outcomes include: changes in use of other illegal drugs or alcohol;changes in CMHC treatment adherence;changes in psychiatric symptoms,quality of life, and community outcomes (homelessness, incarcerations, etc.), nicotine use, and HIV risk status. Further, potential mediators and moderators of the CM paradigm in this population will be studiedand include demographics, psychiatric diagnosis and symptomatology, motivation, stage of change and cognitive function. This proposalis responsive to the NIDA Behavioral and Integrative Treatment Development Program announcement, PA-06-486, for Stage 3 evaluation.